Refractory article and method of making the same



' To all whom it may concern:

' "i-aluminum silicate 1 thus I Patented July 21, 192 5.

UNITED srarss PATENT, OFFICE.

' cnan'nns .r. enrsnn, or rnn'rn AMBOY,

NEW JERSEY, ASSIGNOR TO THE CARBO- BUNDUM. COMPANY, OF NIAGARA. FALLS, NEW YORK, A. OOBPOBATION F PENN- svnvalvmnnriiacronr ARTICLE AND METHOD or name THE SAME.

1T0 Drawing.

Be it known that I, CHARLES F. Gnrcnn,

a citizen of the.United States, residin at tate,

Perth Amboy,c0ujnty of Middlesex, 6 of New Jersey, have invented a new and useful Improvement in Refractory Articles and Methods of Making the Same, of which the following is a full, clear, and exact description.

My invention relates to 'fan, im roved method of bonding silicon carbide or the roduction of refractory articles, such as ricks, furnace linings, etc. Silicon carbide has well known refractory properties 1 and'requires a temperatureabove 2200" G.

to decompose it. It has been used for refractory purposes in two forms, first, as a pure silicon carbide article without a binder as described, for example, in U. S. Patents Nos. 992,698 and 1,013,700, to F. J Tone;

. and second, as silicon carbide grains bonded with a ceramic material as described 1n detail in U. S. Patent No. 1,204,211 to F.

J. :Tone, While the refractory material therein described has been satisfactory for certain types of furnaces, especially those in which only moderately high temperatures are encountered, I have discovered that silicon carbide grains may be bonded together to form refractory shapes by the use of certain inorganic salts or compounds,

which at high temperature in the presence of oxygen react with the silicon carbide to form a high melting compound. This high melting compound then functions as a binder and provides a refractory bodywith "improved refractoriness and resistance to other high temperature conditions.

, Another advantage ofmy roved'silicon carbide article is the desirab e reduction during the firing operation. This is overcome-by the use of suflicient aluminum oxide to react with the silica formedfrom the silicon carbide by oxidation, thus giving "a high. melt' aluminum silicate, such as for example si 'manite AJ,O,, SiO,.- Ihe roduced has marked advantages over t e free silica myself thereto but may use Application filed June 30, 1923. Serial No. 648,827. t Y

.whichwould otherwise be present, in decreasing the tendency to expand and contract, in resistance to erosion by molten slags and inmechanical strength. i

In carrying out my invention, I preferably use silicon carbide ranging in size from 14 mesh to the finest articles. I have found that 40% by weig t of particles 1a to 36 mesh, 20% 36 to 80 mesh, and 40% 80 mesh and finer gives me the maximum density and minimum porosity in my finished article, these roperties being desirable in order to prod resistance to slag penetration. I I v To this mixture of silicon carbide grain, I add, for example, 10 parts of finely divided aluminum oxide. This mixture is tempered with sufiicient water-to bringt it er to the consistency of molding sand, a

which it is subjected to a pressure of a ton or more to. the square inch to form the desired shaped article. It is then dried and fired at high temperature an oxidizing atmosphere. During the burning, some of the sihcon carbide is oxidized to form silicon dioxide and oxides of carbon. The alumina in its finely divided state reacts with the silica and under' suitable condi-' tions forms a bonding material consisting principally of aluminum silicates .or. sillimanite. This bond has a very high melting point and combined with the refractoriness of inert articles of silicon carblde roduces a highly refractory com osite ody. The refractory body thus pro uced serves substantially1 asa solid silicon carwhich excessively high temperatures are encountered. Although I have s alumina in the above i cified the use of ustrated example, 1t

uce great strength. and y will'be understood, that I do not restrict 7 other aluminum compounds as, for example, the hydrates of aluminum, which when heated will react with silica to produce a high melting form ofaluminum silicate such as sillimanite. Iclaim: V .1. The recess of making refractory articles whic includes sil1con 'carb1de with an aluminum compound which w ll react with silica at high temperature to form aluminum silicate, and heating the mixture to a temperature sufiicient to oxidize a portion of the silicon carbide to silica and cause said silica to react,with the aluminum compound to form a high melting silicateof alumina.

2. The process of making refractory articles which includes mixing silicon carbide with alumina and, heating the mixture to a temperature suflicient to oxidize a portion of the silicon carbide to silica and cause said silica to react with the alumina to form sillimanite. L

3. The process of making refractory articles which includes mixing silicon carbide with an aluminum com ound which will react with silica at big tem erature to form aluminum silicate, and mixture to a temperature suflicient to oxidize a portion of the silicon carbide to silica and cause said silica to react with the alu minum compound to form a high melting silicateof alumina, the silicon carbide being substantially by weight of particles, 14 to 36 mesh, 20% 36 to 80 mesh, and 40% 80 mesh or finer.

4. The process of making refractory articles which includes mixing silicon carbide with an aluminum compound which will react with silica at high temperature to form aluminum silicate, and heating the mixture to a temperature sufficient to oxidize a. portion of the silicon carbide to silica and cause said silica to react with the aluminum compound to form a high melting silicate of alumina, the amount of aluminum com-- pound used being substantially 10% by weight of the amount of silicon carbide.

eating the 5. The process of making refractory articles which includes mixing silicon carbide with alumina and heating the mixture to a temperature sufiicient to oxidize a portion of the silicon carbide to silica and cause said silica to react with the alumina to form sillimanite, the silicon carbide being substantially 40% by weight of particles, 14

the mixture into shapes and burning the shaped article.

. 7. As a new article of manufacture a refractory article consisting substantially of silicon carbide, alumina and an aluminum silicate, and containing no graphite.

8. As a new articleof manufacture a refractory article consisting substantially of silicon carbide, free alumina and sillimanite.

9. As a new article of manufacture a re fractory article consistin substantially of finely divided silicon car ide and alumina bonded by sillimanite.

10. A refractory article containin silicon carbide, alumina and a binder pro uced b the reaction of said silicon carbide an. alumina. 1 x

11. As a new article of manufacture a highly refractoryarticle containing at least 80% silicon carbide, and alumina.

In testimony, whereof I have hereunto set my hand.

- CHARLES F. GEIGER. 

